Akademik Veri Yönetim Sistemi
10th International Conference on Fibre-Reinforced Polymer (FRP) Composites in Civil Engineering (CICE), İstanbul, Türkiye, 8 - 10 Aralık 2021, cilt.198, ss.585-596
The ability to numerically predict the ultimate strength of fibre reinforced polymer (FRP) structures is fundamental in order to enable design methodologies not resorting exclusively to experimental tests. In the last few decades, several authors have proposed failure initiation criteria for FRP materials. However, most of the proposed models are either limited in their application range (e.g. valid for unidirectional composites) or require layer-by-layer input data from experimental results that are very difficult to obtain (e.g. strength under biaxial loading). On the other hand, strength predictions based on first ply failure are overly conservative, especially for complex structures where local damage can occur without causing the overall structural collapse. Thereafter, in order to estimate the strength of FRP structures, damage progression models have been associated to failure initiation models. Some authors have adapted damage progression models developed for concrete materials, based on fracture energy. However, owing to the anisotropy and brittle nature of FRP materials, these models require extensive input data from various experimental tests, the values of which may vary widely for different FRP materials. Moreover, finite elements (FE) modelling of damage progression of FRP elements often involves layering the laminates and high computational costs. These limitations lead to the necessity of developing damage progression models able to capture the complex failure behaviour of FRPs while modeling the material as homogenous in order to reduce computational costs. In this paper, a new progressive failure model is proposed for the mesoscale modelling of homogenized FRP composites, considering failure initiation and damage evolution. The quadratic failure initiation model proposed uses two failure indexes, one for inplane and the other for out-of-plane failure. The damage evolution model can be divided in two stages: (i) gradual stiffness loss, and (ii) final failure. In the first stage, the Matzenmiller-Lubliner-Taylor (MLT) exponential damage model is used, attributing different parameters for each elastic and shear moduli. In the second stage, a residual strength is attributed to each direction beyond a limit strain. The progressive failure model was implemented in the FE commercial package ABAQUS through a user material subroutine (UMAT). The results show that the proposed model is able to accurately predict the strength and failure modes of pultruded FRP structures under different loadings, by modeling the laminates as homogeneous orthotropic materials.